hexojs/hexo · error · TypeError

syntax highlighter ${name} is not registered

Error message

syntax highlighter ${name} is not registered

What it means

Thrown by SyntaxHighlight.exec when no highlighter is registered under the requested name. Unlike the other errors this is a runtime lookup failure: exec reads this.store[name] and, finding nothing, reports the engine as unregistered. The message is dynamic and includes the missing name.

Source

Thrown at lib/extend/syntax_highlight.ts:55

  constructor() {
    this.store = {};
  }

  register(name: string, fn: StoreFunction): void {
    if (typeof fn !== 'function') throw new TypeError('fn must be a function');

    this.store[name] = fn;
  }

  query(name: string): StoreFunction {
    return name && this.store[name];
  }

  exec(name: string, options: HighlightExecArgs): string {
    const fn = this.store[name];

    if (!fn) throw new TypeError(`syntax highlighter ${name} is not registered`);
    const ctx = options.context;
    const args = options.args || [];

    return Reflect.apply(fn, ctx, args);
  }
}

export default SyntaxHighlight;

View on GitHub (pinned to 059cb17494)

Solutions

1. Ensure the highlighter plugin that registers the requested name is installed and loaded.
2. Align the config highlight.engine value with a name that was actually registered (check exact spelling/casing).
3. Guard with query(name) before calling exec, falling back to a default highlighter or raw output.

Example fix

// before
hexo.extend.syntax_highlight.exec(engineName, opts);
// after
const fn = hexo.extend.syntax_highlight.query(engineName);
if (fn) hexo.extend.syntax_highlight.exec(engineName, opts);
else return raw; // or exec('default', opts)

const fn = hexo.extend.syntax_highlight.query(name);
if (!fn) return raw; // or fall back to a registered default
hexo.extend.syntax_highlight.exec(name, options);

const isRegistered = (name: string) => typeof hexo.extend.syntax_highlight.query(name) === 'function';

try {
  return hexo.extend.syntax_highlight.exec(name, options);
} catch (e) {
  if (e instanceof TypeError && /is not registered/.test(e.message)) return raw;
  throw e;
}

When it happens

Trigger: Calling exec('prismjs', opts) when 'prismjs' was never registered, or requesting a name with a typo/different casing than what was registered.

Common situations: The highlight config references an engine ('highlight.js' vs 'hljs' vs 'prismjs') that the corresponding plugin did not register, or the highlight plugin is not installed/enabled while the config requests it.

Related errors

• fn must be a function
• fn must be a function
• name is required
• fn must be a function
• name is required

AI-assisted analysis of hexojs/hexo@059cb17494 (2026-08-12). Data as JSON: /api/errors/2b3bb9e1cb2e105e. Report an issue: GitHub.